| Network Working Group | J. Quittek, Ed. |
| Internet-Draft | R. Winter |
| Intended status: Informational | T. Dietz |
| Expires: January 01, 2012 | NEC Europe Ltd. |
| B. Claise | |
| M. Chandramouli | |
| Cisco Systems, Inc. | |
| June 30, 2011 |
Requirements for Energy Management
draft-ietf-eman-requirements-03
This document defines requirements for standards specifications for energy management. Defined requirements concern monitoring functions as well as control functions. Covered functions include identification of powered entities, monitoring of their power state, power inlets, power outlets, actual power, consumed energy, and contained batteries. Further included is control of powered entities' power supply and power state. This document does not specify the features that must be implemented by compliant implementations but rather features that must be supported by standards for energy management.
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With rising energy cost and with an increasing awareness of the ecological impact of running IT and networking equipment, energy management is becoming an additional basic requirement for network management systems and frameworks.
This document defines requirements for standards specifications for energy management. Defined requirements concern monitoring functions as well as control functions. Covered functions include identification of powered entities, monitoring of their power state, power inlets, power outlets, actual power, consumed energy, and contained batteries. Further included is control of powered entities' power supply and power state. Note that this document does not specify the features that must be implemented by compliant implementations but rather features that must be supported by standards for energy management.
The main subject of energy management are powered entities that consume electric energy. Powered entities include devices that have an IP address and can be addressed directly, such as hosts, routers, and middleboxes, as well as devices indirectly connected to an IP network, for which a proxy with an IP address provides a management interface, for example, devices in a building energy management infrastructure using BACNET or MODBUS protocols.
The requirements specified in this document explicitly concern the standards specification process and not the implementation of specified standards. All requirements in this document must be reflected by standards specifications to be developed based on these requirements. But which of the features specified by these standards will be mandatory, recommended, or optional for compliant implementations is to be defined by the concrete standards track document(s) and not in this document.
This document first discusses general objectives of energy management in Section 3. Requirements for an energy management standard are specified in Sections 4 to 8.
The specification of requirements for an energy management standard starts with Section 4 addressing the identification of powered entities and the granularity of reporting of energy-related information. A standard must support unique identification of powered entities. Furthermore, it must support more than just reporting per powered device. Support is required for also reporting energy-related information on individual components of a device or subtended devices. This is why this draft uses the more general term "powered entity" rather than "powered device". An entity may be a device or a component of a device.
Section 5 specifies requirements related to monitoring of powered entities. This includes general (type, context) information and specific information on power states, power inlets, power outlets, power, energy, and batteries. Control power state and power supply of powered entities is covered by requirements specified in Section 6.
At first glance the rather conventional requirements summarized above seem to be all that would be needed for energy management. But it turns out that there are some significant differences between energy management and most of the well known conventional network management functions. The most significant difference from many other management functions is the need to report on others. There are three major reasons for this.
This specific issue of energy management and a set of further ones are covered by requirements specified in Sections 7 and 8.
Electric Energy is needed for operating electric entities. These entities "consume" electric energy by converting it to thermal energy (heat) or other kinds of energy while conducting their operational tasks. For energy management, the total energy converted by an entity during a time interval is of interest.
The term 'energy consumption' is commonly used for both, for referring to the amount of consumed energy and also for referring to the process of consuming energy. In the first case it addresses consumed energy, in the second one it addresses power, typically an average power.
Power is defined as energy conversion rate. For energy management, the instantaneous power of a managed entity may be of interest as well as the average power over a time interval.
A powered entity is a consumer of energy that is subject to energy management. In general, all managed physical entities in a communication network consume electric energy and thus are subject to energy management including particularly energy monitoring and energy control.
A powered entity can be a managed device or a component of a managed device, which is monitored individually.
Power state of an entity is defined as a specific settings of an entity that influences its power. Examples of power states of an entity are on, off, hibernate, and sleep.
Energy management requires retrieving energy-related information on powered entities. In many cases this information is not available at the entities themselves, but at other entities. For example measurement of power and energy consumption can be conducted by power meters at other locations along the power distribution tree for the powered entity.
A power monitor is a module that reports energy-related information on powered entities. A power monitor may be integrated into a powered entity or located remotely of the powered entity. Instances of power monitors may report information on, for example, power supply, power, and power state of a powered entity. There may be multiple power monitors reporting information on the same powered entity.
Powered entities receive power at their power inlets. Powered entities may have multiple inlets, for example, servers with redundant power supply. Examples for power inlets are AC power cords of an entity or an Ethernet port at which the entity receives DC Power over Ethernet (PoE).
Entities may have means to supply others with electrical power. Power is delivered to other entities through power outlets. Power sourcing entities often have more than one power outlet. Examples for power outlets are AC power sockets at a Power Distribution Unit (PDU) and Ethernet ports at a Power over Ethernet (PoE) Power Sourcing Equipment (PSE), that can supply entities with DC power using the Ethernet cable.
Energy management deals with assessing and influencing the consumption of energy in a network of powered entities. A typical objective of energy management is reducing the energy consumption in the network. Ways towards achieving this objective may be limited by other objectives of a general network management system, such as service level objectives.
This document specifies requirements for an energy management standard. This term refers to a collections of documents specifying standards for energy-related monitoring and control. The energy management standard specifies means for building energy management systems.
Requirements specified in this document concern the means that an energy management standard must provide. It does not imply that all required means must be implemented in all energy standard scenarios. Which means and features must be implemented by compliant implementations is to be specified by the energy management standard itself, not by this requirements document.
Note that for meeting individual requirements specified in this document not necessarily new standards are required. It is recommended to rather use existing standards than specify new ones.
The basic objective of energy management is operating communication networks and other equipment with minimal amount of energy, while maintaining a certain level of service. A set of use cases for energy management can be found in [I-D.tychon-eman-applicability-statement].
One approach to achieve this goal is by setting all powered entities to an operational state that results in lower energy consumption, but still meets the service level performance objectives. The sufficient performance level may vary over time and can depend on several factors. In principle, there are four basic types of power states for a powered entity or for a whole system:
In actual implementations the number of power states and their properties vary a lot. Very simple powered entities may just have only the extreme states, full power and power-off state. Some implementations might use IEEE1621 model of three states on, off, and sleep. However, more granular power states can be implemented with many levels of reduced power and/or sleep states.
While the general objective of energy management is quite clear, the way to attain that goal is often difficult. In many cases there is no way of reducing power consumption without the consequence of a potential performance, service, or capacity degradation. Then a trade-off needs to be dealt with between service level objectives and energy efficiency. In other cases a reduction of energy consumption can easily be achieved while still maintaining sufficient service level performance, for example, by switching powered entities to lower power states when higher performance is not needed.
Many energy saving functions can be executed locally by an entity. The basic principle is that an entity monitors its usage and dynamically adapts its energy consumption according to the required performance. In the extreme case, an entity switches to a sleep state when it is not in use at all. Potential interactions with an energy management system for such an entity include the observation of the entity's power state and the configuration of power saving policies, for example, by setting thresholds for power state changes.
Energy savings can also be achieved with policies implemented by a network management system that controls power states of managed entities. In order to make policy decisions properly, information about the energy consumption of entities in different power states is required. Often this information is acquired best through monitoring.
Both methods, network-wide and local energy management, have advantages and disadvantages. In some cases for example, significant energy savings can be achieved by simply setting all entities in a network to sleep, when the network is not needed. However, in general it is dangerous to set all entities of a group to the same state, because there is a risk that such actions ignore specifics of individual entities or violate local service level agreements.
It should be noted that only monitoring energy consumption and power states is obviously not a means to reduce the energy consumption of an entity. In fact, it is likely to increase the power consumption of an entity slightly. The reason is that monitoring energy requires instrumentation that consumes energy when in use. And also reporting of measured quantities over the network consumes energy. However, the acquired energy consumption and power state information is essential for defining energy saving policies and can be used as input to power state control loops that in total can lead to energy savings.
Monitoring operational power states and energy consumption can also be useful for other energy management purposes including but not limited to
From the considerations described above the following basic management functions appear to be required for energy management:
It should be noted that active power control is complementary (but essential) to other energy savings measures such as low power electronics, energy saving protocols (for example, IEEE 802.3az), and energy-efficient device design (for example, sleep and low-power modes for individual components of a device), and energy-efficient network architectures. Measurement of energy consumption may also provide input for developing these technologies.
As already stated Section 1.1, entities on which energy-related information is provided are identified in a sufficiently unique way. This holds in particular for entities that are components of managed devices and in case that one entity reports information on another one, see Section 7. But also for powered entities that control other powered entities it is important to identify the entities they control, see Section 8.
Also stated already in Section 1.1 is the requirement of providing means for reporting energy-related information on components of a managed device. An entity in this document may be an entire managed device or just a component of it. Examples of components of interest are a hard drive, a battery, or a line card. Also for controlling entities it may be useful to be able to address individual components in order to save energy. For example, server blades can be switched off when the overall load is low or line cards at switches may be switched off at night times.
Instrumentation for measuring energy consumption of a device is typically more expensive than instrumentation for retrieving the devices power state. It may be a reasonable compromise in many cases to provide power state information for all individually switchable components of a device separately, while the energy consumption is only measured for the entire device.
Detailed Requirements:
The energy management standard must provide means for uniquely identifying powered entities that are monitored or controlled by an energy management system. Uniqueness must be given in a domain that is large enough to avoid collisions of identities at potential receivers of monitored information.
The energy management standard must provide means for identifying not just entire devices as powered entities, but also individual components of powered devices.
This section describes energy-related information on powered entities for which an energy management standard must provide means for retrieving and reporting.
Note that the fact that an energy management standard provides required means does not imply that all of them must be implemented by every compliant implementation. The concrete specification of standards based on these requirements may label individual features as mandatory, recommended, or optional.
Required information on powered entities can be structured into six groups. Section 5.1 specifies requirements for general information on powered entities, such as type of entity or context information. Section 5.2 covers requirements related to entities' power states. Requirements for information on power inlets and power outlets of powered entities are specified in Section 5.3. Monitoring of power and energy is covered by Sections 5.4 and 5.5, respectively. Finally, Section 5.6 specified requirements for monitoring batteries.
For energy management it is useful to understand role and context of an entity. When monitoring, it may be helpful to group energy consumption per kind of entity. When controlling and setting power states it may be helpful to understand the kind and role of an entity in a network, for example, in order to avoid switching off vital network components.
Detailed Requirements:
The energy management standard must provide means to retrieve and report the type of powered entities.
The energy management standard must provide means for grouping powered entities, for example, into energy monitoring domains, energy control domains, power supply domains, groups of entities of the same type, etc.
The energy management standard must provide means for retrieving and reporting context information on powered entities, for example tags associated with an entity that indicate the entity's role, or importance.
Many entities have a limited number of discrete power states, such as, for example, full power, low power, standby, hibernating, and off.
Obviously, there is a need to report the actual power state of an entity. Beyond that, there is also a requirement for standardizing means for retrieving the list of all supported power states of an entity.
Different standards bodies have already defined their own sets of power states for powered entities. Further organizations are in the process of adding more of these sets. In order to support multiple management systems possibly using different power state sets, while simultaneously interfacing with a particular entity, the energy management standard must provide means for supporting multiple power state sets used simultaneously at a powered entity.
Some of the power states may have parameters that describe the power state with entity's functional capabilities and are represented precisely by numeric values. For example, in low power state, a reduced clock rate may be set to a large number of different values. Since state parameters vary a lot from implementation to implementation it is not considered a requirement to define standards for reporting all those power states parameters. However, it would be useful to have standardized means for reporting some key parameters, such as mean power and maximum power of an entity in a certain state.
There also is a need to report statistics on power states including the time spent an the energy consumed in a power state.
For some network management tasks, it may be desirable to receive notifications from entities, for example, when the components or the entire entity change their power state.
Detailed Requirements:
The energy management standard must provide means for reporting the actual power state of an entity.
The energy management standard must provide means for retrieving the list of all potential power states of an entity.
The energy management standard must provide means for supporting multiple power state sets simultaneously at a powered entity.
The energy management standard must provide means for retrieving the list of all power state sets supported by an entity.
Referring to the "list of supported power state sets" requirement, the energy management standard must provide means for retrieving the list of all potential power states of an entity that belong to a given power state set.
The energy management standard must provide means for retrieving the maximum power and the average power as a typically static property for each supported power state.
The energy management standard must provide means for monitoring statistics per power state including at least the total time spent in a power state, the number of times a state was entered and the last time a state was entered. More power state statistics are addressed by requirement 5.5.3.
The energy management standard must provide means for generating a notification when the actual power state of a powered entity changes.
Powered entities have power inlets at which they are supplied with electric power. Many entities just have a single power inlet, while others have multiple ones. Often different power inlets are connected to separate power distribution trees. For energy monitoring, it is important information which power inlets an entity has, if power is available at an inlet and which of them are actually in use.
Some entities have power outlets for supplying other entities with electric power. An entity may have multiple power outlets. Examples are a Power Distribution Units (PDU) and a Power over Ethernet (PoE) Power Sourcing Equipment (PSE).
For identifying and potentially controlling the source of power received at an inlet, it is useful to identify the power outlet of another entity at which the received power is provided. Analogously, for each outlet it is of interest to identify the power inlets that receive the power provided at a certain outlet.
Static properties of each power inlet and each power outlet are useful information for energy management. Static properties include the kind of electric current (Alternating Current (AC) or Direct Current (DC)), the nominal voltage, the nominal AC frequency, and the number of AC phases.
Detailed Requirements:
The energy management standard must provide means for monitoring the list of power inlets and power outlets at an entity.
The energy management standard must provide means for identifying the power outlet that provides the power received at a power inlet.
The energy management standard must provide means for identifying the list of power inlets that receive the power provided at a power outlet.
The energy management standard must provide means for monitoring the availability of power at each power inlet and each power outlet. This information indicates whether at a power providing outlet power supply is switched on or off.
The energy management standard must provide means for monitoring for each power inlet and each power outlet if it is in actual use. For the inlet this means that the entity actually receives power at the inlet. For the outlet this means that actually power is provided to one or more entities at the outlet.
The energy management standard must provide means for reporting the type of current (Alternating Current (AC) or Direct Current (DC) for each power inlet and each power outlet of a powered entity.
The energy management standard must provide means for reporting the nominal voltage for each power inlet and each power outlet of a powered entity.
The energy management standard must provide means for reporting the nominal AC frequency for each power inlet and each power outlet of a powered entity.
The energy management standard must provide means for reporting the number of AC phases for each power inlet and each power outlet of a powered entity.
Power is a quantity measured as instantaneous power or as average power over a time interval. In contrast to power state values, this quantity may change continuously.
Obtaining highly accurate values for power and energy may be costly. Often dedicated metering hardware is needed for this purpose. Entities without the ability to measure their power and energy consumption with high accuracy may just report estimated values, for example based on load monitoring or even just the entity type.
Depending on how power and energy consumption values are obtained the confidence in the reported value and its accuracy may vary. Entities reporting such values should qualify the confidence in the reported values and quantify the accuracy of measurements. For reporting accuracy, the accuracy classes specified in IEC 62053-21 [IEC.62053-21] and IEC 62053-22 [IEC.62053-22] should be considered.
In addition to the plain real power value, also further properties of the supplied power are subject to monitoring. In case of AC power supply, there are more power values beyond the real power to be reported including the apparent power, the reactive power, and the phase angle of the current or the power factor. For both AC and DC power the power quality is also subject of monitoring. Power quality parameters include the actual voltage, the actual frequency, the Total Harmonic Distortion (THD) of voltage and current, the impedance of an AC phase or of the DC supply. Power quality monitoring should be in line with existing standards, such as [IEC.61850-7-4].
For some network management tasks, it is required to obtain time series of power values (or energy consumption values). In general these could be obtained in many different ways. It should be avoided that such time series can only be obtained by regular polling by the energy management system. Means should be provided to either push such values from the place they are available to the management system or to have them stored at the entity for a sufficiently long period of time such that a management system can retrieve a stored time series of values.
Detailed Requirements:
The energy management standard must provide means for reporting the real power for each power inlet and each power outlet of a powered entity.
The energy management standard must provide means for reporting the confidence in reported power values by indicating the way these values have been obtained. for example, by power measurement, by estimation based on performance values, or hard coding average power values for a powered entity.
The energy management standard must provide means for reporting the accuracy of reported power values.
The energy management standard must provide means for reporting the complex power for each power inlet and each power outlet of a powered entity. Besides the real power, at least two out of the following three quantities need to be reported: apparent power, reactive power, phase angle. The phase angle can be substituted by the power factor. In case of AC power supply, means must be provided for reporting the complex power per phase.
The energy management standard must provide means for reporting the actual voltage and actual current for each power inlet and each power outlet of a powered entity. In case of AC power supply, means must be provided for reporting the actual voltage and actual current per phase.
The energy management standard must provide means for reporting the actual AC frequency for each power inlet and each power outlet of a powered entity.
The energy management standard must provide means for reporting the Total Harmonic Distortion (THD) of voltage and current for each power inlet and each power outlet of a powered entity. In case of AC power supply, means must be provided for reporting the THD per phase.
The energy management standard must provide means for reporting the impedance of power supply for each power inlet and each power outlet of a powered entity. In case of AC power supply, means must be provided for reporting the impedance per phase.
The energy management standard must provide means for collecting time series of real power values for each power inlet and for each power outlet of an entity without requiring to regularly poll the entity from an energy management station. A solution for this is that the concerned entity or another entity closely interacting with the concerned entity collect time series of power values and make them available via push or pull mechanisms to receivers of the information.
Monitoring of electrical energy consumed (or converted) at an entity can be done in various ways. One is collecting time series of power values for the entity and calculating the consumed energy from these values. an alternative is the entity itself or another entity taking care of energy measurement and reporting energy consumption values for certain time intervals. Time intervals of interest are the time from the last restart of the entity to the reporting time, the time from another past event to the reporting time, or the last given amount of time before the reporting time.
In order to monitor energy consumption in different power states, it is useful if entities record their energy consumption per power state and report these quantities.
For some network management tasks, it is required to obtain time series of energy values. In general these could be obtained in many different ways. It should be avoided that such time series can only be obtained by regular polling by the energy management system. Means should be provided to either push such values from the place they are available to the management system or to have them stored at the entity for a sufficiently long period of time such that a management system can retrieve a stored time series of values.
Detailed Requirements:
The energy management standard must provide means for reporting the consumed energy received at a power input or provided at a power outlet of an entity. Reports must be made for a clearly specified time interval.
The energy management standard must provide means for reporting the consumed energy of an entity for certain time intervals.
The energy management standard must provide means for reporting the consumed energy individually for each power state. This extends the requirement 5.2.7 on power state statistics.
The energy management standard must provide means for collecting time series of energy values for each power inlet and for each power outlet of an entity without requiring to regularly poll the entity from an energy management station. A solution for this is that the concerned entity or another entity closely interacting with the concerned entity collect time series of energy values and make them available via push or pull mechanisms to receivers of the information.
Today more and more powered entities contain batteries that supply them with power when disconnected from electrical power distribution grids. Common examples are nomadic and mobile devices, such as notebook computers, netbooks, and smart phones. The status of batteries in such an entity, particularly the charging status is typically controlled by automatic functions that act locally on the entity and manually by users of the entity. In addition to this, there is a need to monitor the battery status of these entities by network management systems.
The management requirements discussed above in Sections 5.1 to 5.5 concern energy-related information on entities. Entities may be powered devices or components of powered devices. Devices containing batteries can be modeled in two ways. The entire device can be modeled as a single entity on which energy-related information is reported or the battery can be modeled as an individual entity for which energy-related information is monitored individually according to requirements in Sections 5.1 to 5.5.
In both cases further information on batteries is of interest for energy management, such as the current charge of the battery, the number of completed charging cycles, the charging state of the battery, and further static and dynamic battery properties. Also desirable is to receive notifications if the charge of a battery becomes very low or if a battery needs to be replaced.
Detailed Requirements:
The energy management standard must provide means for reporting the current charge of a battery.
The energy management standard must provide means for reporting the charging state (charged, discharged, etc.) of a battery.
The energy management standard must provide means for reporting the number of completed charging cycles of a battery.
The energy management standard must provide means for reporting the actual capacity of a battery.
The energy management standard must provide means for reporting static properties of a battery, including the nominal capacity, the number of cells, the nominal voltage, and the battery technology.
The energy management standard must provide means for generating a notification when a the charge of a battery decreases below a given threshold.
The energy management standard must provide means for generating a notification when the number of charging cycles of battery exceeds a given threshold.
The energy management standard must provide means for meeting requirements 5.6.1 to 5.6.7 for each individual battery contained in a single entity.
Many entities control their power state locally by self-managed dynamic adaptation to the environment. But other entities without that capability need interfaces for a energy management system to control their power states in order to save energy. Even for self-managed entities such interface may be useful for overruling local policy decisions by global ones from an energy management system.
Power supply is typically not self-managed by powered entities. And controlling power supply is typically not conducted as interaction between energy management system and the powered entity itself. It is rather an interaction between the management system and an entity providing power at its power outlets. Still, requirements for power state control apply accordingly to power supply control.
Note that shutting down the power supply abruptly may have severe consequences for the powered entity.
Detailed Requirements:
The energy management standard must provide means for setting power states of powered entities.
The energy management standard must provide means for switching power supply off or turning power supply on at power outlets providing power to one or more powered entity.
As already discussed in the introduction of Section 5, not all energy-related information may be available at the concerned powered entity. Such information may be provided by other entities, such as a Power Distribution Unit (PDU), external power meter, or a Power over Ethernet (PoE) Power Sourcing Equipment (PSE). Some of these entities (PDU, PSE) can also control the power provided to the other powered entities, while some can just report on the remote powered entities (external power meter). This section covers reporting of information (monitoring) only. Please see Section 8 for requirements on controlling other entities
There are cases where a power supply unit switches power for several powered entities by turning power on or off at a single power outlet or where a power meter measures the accumulated power of several entities at a single power line. Consequently, it should be possible to report that a monitored value does not relate to just a single powered entity, but is an accumulated value for a set of powered entities. All of these entities belonging to that set need to be identified.
If a powered entity has information about where energy-related information on itself can be retrieved, then it would be very useful if it has a way to communicate this information to an energy management system. This applies even if the information only provides accumulated quantities for several powered entities.
Detailed Requirements:
The energy management standard must provide means for an entity to report energy-related information on another entity.
The energy management standard must provide means for reporting the identity of another entity on which energy-related information is reported.
For entities reporting single values that are accumulated over multiple entities, the energy management standard must provide means for reporting the list of all entities from which contributions are included in the accumulated value.
The energy management standard must provide means for an entity to report the list of all other entities on which it can report energy-related information.
The energy management standard must provide means for an entity to indicate for each other entity on which it can provide energy-related information which energy-related information can be provided for this entity.
The energy management standard must provide means for a powered entity to indicate another entity at which energy-related information on itself can be retrieved.
For a powered entity that has another entity at which energy-related information on itself can be retrieved, the energy management standard must provide means for indicating the information that is available at other entities per other entity.
This section specifies requirements for controlling power states and power supply of powered entities by communicating not with these entities themselves, but with other entities that have means for controlling power state or power supply of others.
Some entities may have control of power states of other entities. For example a gateway to a building network may have means to control the power state of entities in the building that do not have an IP interface. For this and similar cases means are needed to make this control accessible to the energy management system.
In addition to this, it is very useful that an entity that has its state controlled by other entities has means to report the list of these other entities.
Detailed Requirements:
The energy management standard must provide means for an energy management system to send power state control commands to entity that concern the power states of other entities than the one the command was send to.
The energy management standard must provide means for reporting the identity of another entity for which the reporting entity has means to control the power state.
The energy management standard must provide means for an entity to report the list of all entities for which it can control the power state.
The energy management standard must provide means for an entity that has receives commands controlling its power state from other entities to report the list of all those entities.
Some entities may have control of the power supply of other entities, for example, because the other entity is supplied via a power outlet of the entity. For this and similar cases means are needed to make this control accessible to the energy management system.
In addition to this, it is very useful that an entity that has its supply controlled by other entities has means to report the list of these other entities.
Detailed Requirements:
The energy management standard must provide means for an energy management system to send power supply control commands to entity that concern the power supply of other entities than the one the command was send to.
The energy management standard must provide means for reporting the identity of another entity for which the reporting entity has means to control the power supply.
The energy management standard must provide means for an entity to report the list of all other entities for which it can control the power supply.
The energy management standard must provide means for an entity that has other entities controlling its power supply to report the list of all those entities.
The typical security threats for the management protocol for energy monitoring are similar to the ones specified in the SNMP security framework. In other words, from an energy monitoring point of view, no additional security requirements have been imposed.
Link layer discovery mechanisms need to ensure that only the trusted entities shall be discovered during discovery and detect/discard entities without a trusted relationship to be included among the entities for energy monitoring.
In terms of monitoring, considering that there can be some network entities which shall be entitled to collect the measured data on behalf of other entities, then it is important to authenticate and/or authorize such entities. In addition, in the case of control of other entities, it would be highly desirable to have some form of an authentication mechanism to ensure that only the designated entities shall control the entities within its control domain. It should be possible to prevent an entity which does not have the appropriate authorization and authority to control or configure entities in its control domain/purview. Secondly, it should be possible to prevent malicious entities exercising control over entities.
This document has no actions for IANA.
The authors would like to thank Ralf Wolter for his first essay on this draft. Many thanks to William Mielke and John Parello for helpful comments on the draft.
For some network management tasks it may be desirable to receive notifications from entities when the power of an entity exceeds or falls below certain thresholds. Do we want to make this a requirement?
Proposal: added "for example" so that we don't restrict the framework to only this notification
We have requirements for reporting of time series of power and energy values. Do we need both or just one of them? If just one, then which one?
How to model the case that an inlet or outlet changes during operation from one kind to the other. An example is a battery that receives power at a socket at one time. Then the socket is an inlet. At another time the battery provides power at the same socket. Then it's an outlet. The same holds for entities with integrated power generators.
One solution would be to introduce a new kind of hybrid in/outlets. Another one would be to model the same socket as inlet as well as as outlet. It would appear twice in the list of all inlets and outlets. Then received power/energy would be reported under the inlet entry and provided power/energy would be reported under the outlet entry.
These would be two solutions. What would be the concrete requirement behind them?
Aggregation functions are not covered (yet). Are there requirements on aggregation? Which are they?
References to mentioned IEC standards are missing. Also these references should be double checked.
Section 1 mentions BACNET or MODBUS as examples for building network protocols. We need references to the standards specifications for these protocols.
A reference to the IEEE 1621 standard is missing in section 3.1 and a reference to IEEE 802.3az is missing in section 3.4. The references should be double checked if they are well applicable in the respective section.
Is there an IEC standard on DC power quality?
This section analyzes existing standards for energy consumption and power state monitoring. It shows that there are already several standards that cover only some part of the requirements listed above, but even all together they do not cover all of the requirements for energy management.
There are already RFCs available that address a subset of the requirements.
The ENTITY-MIB module defined in [RFC4133] was designed to model physical and logical entities of a managed system. A physical entity is an identifiable physical component. A logical entity can use one or more physical entities. From an energy monitoring perspective of a managed system, the ENTITY-MIB modeling framework can be reused and whenever RFC 4133 [RFC4133] has been implemented. The entPhysicalIndex from entPhysicalTable can be used to identify an entity/component. However, there are use cases of energy monitoring, where the application of the ENTITY-MIB does not seem readily apparent and some of those entities could be beyond the original scope and intent of the ENTITY-MIB.
Consider the case of remote devices attached to the network, and the network device could collect the energy measurement and report on behalf of such attached devices. Some of the remote devices such as PoE phones attached to a switch port have been considered in the Power-over-Ethernet MIB module [RFC3621]. However, there are many other devices such as a computer, which draw power from a wall outlet or building HVAC devices which seem to be beyond the original scope of the ENTITY-MIB.
Yet another example, is smart-PDUs, which can report the energy consumption of the device attached to the power outlet of the PDU. In some cases, the device can be attached to multiple to power outlets. Thus, the energy measured at multiple outlets need to be aggregated to determine the consumption of a single device. From mapping perspective, between the PDU outlets and the device this is a many-to-one mapping. It is not clear if such a many-to-one mapping is feasible within the ENTITY-MIB framework.
RFC 4268 [RFC4268] defines the ENTITY STATE MIB module. Implementations of this module provide information on entities including the standby status (hotStandby, coldStandby, providingService), the operational status (disabled, enabled, testing), the alarm status (underRepair, critical, major, minor, warning), and the usage status (idle, active, busy). This information is already useful as input for policy decisions and for other network management tasks. However, the number of states would cover only a small subset of the requirements for power state monitoring and it does not provide means for energy consumption monitoring. For associating the information conveyed by the ENTITY STATE MIB to specific components of a device, the ENTITY STATE MIB module makes use of the means provided by the ENTITY MIB module [RFC4133]. Particularly, it uses the entPhysicalIndex for identifying entities.
The standby status provided by the ENTITY STATE MIB module is related to power states required for energy management, but the number of states is too restricted for meeting all energy management requirements. For energy management several more power states are required, such as different sleep and operational states as defined by the Advanced Configuration and Power Interface (ACPI) [ACPI.R30b] or the DMTF Power State Management Profile [DMTF.DSP1027].
RFC 3433 [RFC3433] defines the ENTITY SENSOR MIB module. Implementations of this module offer a generic way to provide data collected by a sensor. A sensor could be an energy consumption meter delivering measured values in Watt. This could be used for reporting current power of an entity and its components. Furthermore, the ENTITY SENSOR MIB can be used to retrieve the accuracy of the used power meter.
Similar to the ENTITY STATE MIB module, the ENTITY SENSOR MIB module makes use of the means provided by the ENTITY MIB module [RFC4133] for relating provided information to components of a device.
However, there is no unit available for reporting energy quantities, such as, for example, watt seconds or kilowatt hours, and the ENTITY SENSOR MIB module does not support reporting accuracy of measurements according to the IEC / ANSI accuracy classes, which are commonly in use for electric power and energy measurements. The ENTITY SENSOR MIB modules only provides a coarse-grained method for indicating accuracy by stating the number of correct digits of fixed point values.
RFC 1628 [RFC1628] defines the UPS MIB module. Implementations of this module provide information on the current real power of entities attached to an uninterruptible power supply (UPS) device. This application would require identifying which entity is attached to which port of the UPS device.
UPS MIB provides information on the state of the UPS network. The MIB module contains several variables that are used to identify the UPS entity (name, model,..), the battery state, to characterize the input load to the UPS, to characterize the output from the UPS, to indicate the various alarm events. The measurements of power in UPS MIB are in Volts, Amperes and Watts. The units of power measurement are RMS volts, RMS Amperes and are not based on Entity-Sensor MIB [RFC3433].
Similar to the UPS MIB, implementations of the POWER ETHERNET MIB module defined in RFC3621 [RFC3621] provide information on the current energy consumption of the entities that receive Power over Ethernet (PoE). This information can be retrieved at the power sourcing equipment. Analogous to the UPS MIB, it is required to identify which entities are attached to which port of the power sourcing equipment.
The POWER ETHERNET MIB does not report power and energy consumption on a per port basis, but can report aggregated values for groups of ports. It does not use objects of the ENTITY MIB module for identifying entities, although this module existed already when the POWER ETHERNET MIB modules was standardized.
The Link Layer Discovery Protocol (LLDP) defined in IEEE 802.1ab is a data link layer protocol used by network devices for advertising of their identities, capabilities, and interconnections on a LAN network. The Media Endpoint Discovery (MED) (ANSI/TIA-1057) is an enhancement of LLDP known as LLDP-MED. The LLDP-MED enhancements specifically address voice applications. LLDP-MED covers 6 basic areas: capabilities discovery, LAN speed and duplex discovery, network policy discovery, location identification discovery, inventory discovery, and power discovery.
The DMTF has defined a power state management profile [DMTF.DSP1027] that is targeted at computer systems. It is based on the DMTF's Common Information Model (CIM) and rather an entity profile than an actual energy consumption monitoring standard.
The power state management profile is used to describe and to manage the power state of computer systems. This includes e.g. means to change the power state of an entity (e.g. to shutdown the entity) which is an aspect of but not sufficient for active energy management.
ODVA is an association consisting of members from industrial automation companies. ODVA supports standardization of network technologies based on the Common Industrial Protocol (CIP). Within ODVA, there is a special interest group focused on energy and standardization and inter-operability of energy aware entities.
The charter of the IEEE-ISTO Printer Working Group is for open standards that define printer related protocols, that printer manufacturers and related software vendors shall benefit from the interoperability provided by conformance to these standards. One particular aspect the Printer WG is focused on is power monitoring and management of network printers and imaging systems PWG Power Management Model for Imaging Systems [IEEE-ISTO]. Clearly, these devices are within the scope of energy management since these devices consume power and are attached to the network. In addition, there is ample scope of power management since printers and imaging systems are not used that often. IEEE-ISTO Printer working group has defined MIB modules for monitoring the power consumption and power state series that can be useful for power management of printers. The energy management framework should also take into account the standards defined in the Printer working group. In terms of other standards, IETF Printer MIB RFC3805 [RFC3805] has been standardized, however, this MIB module does not address power management of printers.